【HM12.0】Data structure and access method

• LCU vs. Sub-CU

–All CUs are handled throughTComDataCU* pointer（所有CU是通过 TComDataCU *指针操作处理）

–From the LCU (largest CU), Sub-CUis processed recursively by z-scan（CU通过Z顺序扫描）

• TComDataCU class has all information we need 

  – Actual data storage is allocated only at LCU (largest CU) level

    • In Sub-CUs, data storage points to suitable position in LCU storage

• Every information in CU is accessed by index （CU中信息的访问方式依靠索引号）

   –Basically, every index is the storage unit number within the CU

   –In source-code,AbsPartIdx means absolute index in the given CU （代码中AbsPartIdx代表CU内单元的索引号）

• How to obtain absolute index in LCU?（LCU内单元的索引获取方式（通过m_uiAbsIdxInLCU））

  – EachTComDataCU class hasm_uiAbsIdxInLCU, which means the absolute z-scanindex in LCU basis

  – Useful to derive index ofneighbouring CUs

 • How to convert between z-scan and raster scan in LCU-basedindex?(Z扫描与光栅扫描转换)

   –Two arrays,g_auiZscanToRaster andg_auiRasterToZscan

   –g_auiZscanToRaster[ z-scan index ] = raster scanindex

   –g_auiRasterToZscan[ raster index ] = z-scan index

    Raster scan is useful to derive index ofneighbouring CUs

• Transform coefficient data structure （变换后系数数据结构）

   –1D arrays,m_pcTrCoeffY,m_pcTrCoeffCb andm_pcTrCoeffCr are allocated in LCU

      For each CU, getCoeffY, getCoeffCb and getCoeffCr give the starting point of coefficients. They are arranged         using  raster-scan